1. Field of the Invention
This invention relates to a system for managing production of semiconductor devices and, more particularly, to a system for managing conditions on a production line for producing semiconductor devices.
2. Description of the Related Art
FIG. 2 is a schematic block diagram of a conventional production line for producing semiconductor devices. The production line 1 has a plurality of production apparatus 11a disposed therealong and inspection apparatus 11b which are suitably arranged between adjacent production apparatus 11a. The production apparatus 11a effect various processes or treatments on successive semiconductor wafers. The processes and treatments include, for example, ion implantation, oxidation, diffusion, sputtering of Al or other materials, deposition of dielectric materials, etching and pattern exposure. The inspection apparatus 11b inspects partially finished products which have been prepared by the production apparatus which is immediately upstream thereof. For example, the inspection apparatus is intended for measurement of the sheet resistance, film thickness and so forth.
These production apparatus 11a and the inspection apparatus 11b operate in accordance with predetermined production conditions and inspection conditions which are set in the corresponding recipes 3.
In operation, each of the semiconductor wafers 2 introduced onto the production line 1 undergoes various processes or treatment which are performed by the production apparatus 11a in accordance with production conditions set in the recipes 3, as well as inspections performed by the inspection apparatus 11b in accordance with various inspection conditions set in the corresponding recipes 3. A desired semiconductor device is obtained when the semiconductor wafer 2 has passed through all the production apparatus 11a and the inspection apparatus 11b, and comes off the production line 1.
Then, the product undergoes an evaluation performed by an evaluation apparatus (not shown) which measures characteristics such as the threshold level, current driving capacity and so forth, thus evaluating the quality and performance of the product semiconductor device. The measurement and evaluation cannot be executed unless the production proceeds to the final process.
In general, however, errors in the prescribed accuracy in the production apparatus 11a and the inspection apparatus 11b often occur or they may fail to exactly perform the expected operations for some reason. It is to be noted that, in the conventional production line, the production apparatus and the inspection apparatus are allowed to operate independently, regardless of errors and malfunctions in the production apparatus 11a and the inspection apparatus 11b. This means that, even though an upstream production apparatus 11a has failed to execute an expected operation, the production apparatus 11a of the next stage, i.e., the downstream production apparatus 11a, is allowed to conduct ordinary operations in accordance with the conditions set in the recipe 3. This conventional production line, therefore, involves a large risk of the product semiconductor device being rejected due to unacceptably low quality or performance. In such a case, the operation of the downstream production apparatus 11a is useless. Further, although it is possible to reject any poor product during the production steps if it is detected by any one of the inspection apparatus, such rejection will seriously impair production yield.